1. Field
This invention pertains to endoscopes in general and to arthroscopes in particular. Specifically, it provides such an instrument in a configuration ideal for use in arthroscopy.
2. State of the Art
Endoscopy is the art of examining the interior of a body cavity or hollow organ by the use of a slender tubular telescopic instrument called an "endoscope ". Endoscopes have been in common use since the early twentieth century. These instruments include a lens system, which may be conventional glass lenses within a rigid tube, air spaces between glass rods shaped to configurate the entrapped air pockets as lenses, optical glass fibers combined with conventional lenses, or other means; and a lighting system, which may be a direct illumination system (e.g., a tungsten light bulb) but is more often fiber light (light transferred from an external source through optical glass fibers). Endoscopes also commonly contain an irrigation system for introducing fluids, typically normal saline solution, to the region being examined. These systems are all contained within a cylindrical tubular housing, usually called a "sheath", which may be flexible, but is more often rigid. The cross-sectional configuration of the sheath normal its longitudinal axis (that is, as viewed from the distal end of the endoscope) is traditionally circular.
Examples of modern endoscopes are disclosed by U.S. Pat. Nos. 3,525,332; 3,599,630; 3,608,547; 3,730,632; 3,744,906; 3,818,902; 3,819,267; and 3,889,662.
Endoscopes have been used for arthroscopic examinations for several decades. The development of arthroscopy and instruments adopted for arthroscopic examinations (arthroscopes) is described in the monograph "Arthroscopy of the Knee", Robert W. Jackson and David J. Dandy, Modern Orthopedic Monographs, 1976 Grune & Stratton, Inc., New York. From the monograph, it is apparent that the principal objective sought in developing arthroscopes has been to reduce their diameter compared to earlier endoscopes. All of the components conventional to an endoscope, namely an optical system, a lighting system, an irrigation system, and often an instrument channel, are contained within a usually rigid cylindrical sheath of approximately circular cross-section. The Watanabe 22 shown in FIGS. 2-5 of the monograph utilizes a sheath slightly oval in cross-section to accommodate two crescentic bundles of light fibers for illumination. The grouping of the light fibers in this fashion is to avoid the penumbra typically present in the center of the visual field.
Examination of the knee joint, or other joints, imposes certain restrictions on procedures not normally encountered with other endoscopic examinations. For example, a persistent problem in arthroscopy has been maintaining adequate sterility. A circular cross-section is appropriate for introducing into the orifices of the genitourinary and gastrointestinal tracts or for puncturing the abdominal wall, but the introduction of conventional round arthroscopes to the knee joint tends to be traumatic because of the limited spacing between bones. Conventional arthroscopes of small cross-section are susceptible of breakage if the knee is flexed or if too much force is applied in efforts to distract the joint using the arthroscope as a lever or fulcrum. In the past, less delicate arthroscopes have necessarily been constructed within sheaths of greater diameter.